Objective: to learn how to control the growth of asparagine- synthesizing mouse lymphoma cells in vivo. Methods and Materials: I propose to continue studying factors that influence the growth and regression in vivo of two closely related lines of mouse lymphoma cells: a) our"cloned" Lymphoma 6C3HED-OG "C" cells, which require exogenous asparagine for protein synthesis and growth and are regularly controllable with asparaginase; and b) our "cloned" Lymphoma 6C3HED-RG "C" cells, which do not require exogenous asparagine for protein synthesis and growth and which, like the generality of mammaliam cancer cells, are largely uncontrollable with asparaginase (or otherwise). In addition, I propose to continue studying factors that influence the growth of cultured HeLa cells-this as a useful in vitro experimental model of asparagine-synthesizing mammalian cancer cells.